The Present Application relates, generally, to a heat pipe for cooling exothermic bodies such as semiconductor integrated circuits, LED elements and power devices, a method for manufacturing the heat pipe and circuit boards with the heat pipe function.
Electronic devices such as semiconductor integrated circuits, LED elements and power devices are used for electronic equipment, industrial equipment and automobiles. These electronic parts are exothermic bodies that generate heat by the current flowing inside. When exothermic bodies are heated to a give temperature or above, the operation may not be guaranteed, or other parts and the housing may be adversely influenced. As a result, the performance of electronic equipment and industrial equipment may be deteriorated.
In order to cool such exothermic bodies, some heat pipes have been proposed that have the cooling effects by the vaporization and condensation of enclosed cooling media.
On the other hand, there is a need for the high-density packaging of electronic parts and elements because electronic equipment and industrial equipment have been miniaturized. Since only one side of it is brought into contact with an electronic part or an element, a heat pipe may occupy an unnecessary capacity in electronic equipment. In the case that electronic parts, which are exothermic bodies, are smaller in size than a heat pipe, it may be difficult for electronic parts other than those to be cooled to be mounted at the place where the heat pipe is installed. As a result, the heat pipe may prevent the high-density packaging. Or, the cooling capacity of the heat pipe may not be fully utilized.
Some technologies have been proposed for enhancing the packaging density, wherein through-holes are formed on a metal core printed circuit board having a cooling function. See, for example, Japanese Patent Application No. 2007-242740. Some technologies for facilitating the mounting of heat pipes have also been proposed. See, for example, Japanese Patent Application No. 2004-037001. Moreover, some technologies for providing a concave curved section on the surface of a heat pipe have been proposed for enhancing the cooling performance of the heat pipe and utilizing the surface. See, for example, Japanese Patent Application No. H11-101585.
In the '240 Application, a via hole having a small diameter is formed after performing the thin wall processing on a metal core layer. In this case, since the via hole is formed after pasting insulating layers on both surfaces of the thin wall processed metal core layer, the position of the via hole may be shifted when the thin wall section is too thin. Moreover, it is difficult to process a heat pipe whose inside is hollow (the inside of a heat pipe is hollow for the purpose of enclosing a cooling medium) unlike a metal core layer. This is because the position and shape of a via hole may be shifted by the pressure put on the metal board sections on the upper and lower layers of the cavity. Accordingly, it is difficult to apply the technology for forming a via hole after providing a metal core layer with a thin wall section to the formation of a via hole in a heat pipe.
The '001 Application can facilitate the mounting of a heat pipe. However, other electronic parts cannot be mounted on the place where a heat pipe is mounted. Hence, the problem that a heat pipe may inhibit the high-density packaging cannot be solved. In addition, there is another problem that the enclosure of the inner space may be destroyed at the time of forming a via hole on the outer peripheral section of a heat pipe.
The '585 Application enables to mount electronic parts along the curved section of a heat pipe. However, this is limited to the lead wiring along the curved section. In reality, it is difficult to mount electronic parts on a heat pipe.
None of these references, however, enables to realize a heat pipe that does not prevent the high-density packaging. Particularly, as there may be an increasing need for enhancing the cooling capability in the future, it is inevitable that the size of a heat pipe increases. Thus, there is a need for a heat pipe that does not prevent the high-density packaging even when its size is increased.